East Coast braces for Hurricane Irene

Note: This post has been updated to reflect ongoing developments.

New York City--along with much of the East Coast--is bracing for Hurricane Irene.

The city is ready to evacuate low-lying areas and will use police boats to rescue stranded residents if necessary, Mayor Michael Bloomberg said Thursday. Neighboring New Jersey has declared a state of emergency.

UPDATE: Gov. Andrew Cuomo of New York has now declared a state of emergency as well.

The Category 3 hurricane slammed into the Bahamas today. Forecasters expect it to move up the east coast, where it could hit New York City by late Saturday or Sunday. It will likely have weakened to a Category 2 storm by then.

This map, put together by WNYC, shows New Yorkers which areas of the city are most at risk.

Because this month has already been rainy in the northeast, there's a higher risk of Irene causing flooding and fallen trees in the region. New Jersey has received twice as much rain as in a normal August.

On the North Carolina coast, where Irene is expected to make landfall Saturday, thousands fled their homes. Governor Bev Perdue has declared a state of emergency, and local authorities have told about 180,000 people to leave the area.

In Virginia, dozens of Navy ships have left their ports, planning to ride out the storm at sea.

Federal officials are urging people in low-lying areas up and down the east coast to take precautions. Those include putting together an emergency kit with food and water for 3 days, developing a family communications plan, and listening to TV or radio to hear about evacuations.

Already, on Acklins Island in the Bahamas, 90 percent of the homes on the Lovely Bay settlement were destroyed Wednesday after Irene swept through. And two people in Haiti were killed when they were swept away by raging waters caused by heavy rain connected with the hurricane.

Even air travelers may be affected. "You're going to start seeing (flight) cancellations," Anne Banas of SmarterTravel.com told CNN. "People should just be prepared."